Drop on demand ink jet technology is widely used in the printing industry. Printers using drop on demand ink jet technology can use either thermal ink jet technology or piezoelectric technology. Even piezoelectric ink jet devices are more expensive to manufacture than thermal ink jet devices, piezoelectric ink jets are generally favored as they can use a wider variety of inks.
Piezoelectric ink jet print heads typically include a flexible diaphragm and a piezoelectric element attached to the diaphragm. When a voltage waveform is applied to the piezoelectric element, typically through electrical connection with an electrode electrically coupled to a voltage source, the piezoelectric element oscillates, causing the diaphragm to oscillate. Consequently, this will expel a quantity of ink from a chamber through a nozzle. The oscillation further draws ink into the chamber from a main ink reservoir through an opening to replace the expelled ink.
Increasing the printing resolution of an ink jet printer employing piezoelectric ink jet technology is a goal of design engineers. Increasing the jet density of the piezoelectric ink jet print head can increase printing resolution. One way to increase the jet density is to eliminate manifolds which are internal to a jet stack. With this design, it is preferable to have a single port through the back of the jet stack for each jet. The port functions as a pathway for the transfer of ink from the reservoir to each jet chamber. Because of the large number of jets in a high density print head, the ink inlets must pass vertically through the diaphragm and between the piezoelectric elements.
Manufacturing a high density ink jet print head assembly having an external manifold has required new processing methods. Piezoelectric ink jet print heads with an external manifold require ink inlets to pass through the electronic portion of the print head assembly. Assembly methods for a print head having an electrical interconnect layer that is easier to manufacture than prior assemblies would be desirable.